l\  S.  DEPARTMENT  OF  AGRICULTURE, 

BUREAU   01   KNTOMoUk.Y  — CIRCULAR  No.  162. 

I      ()     HOW  \KD.    I  nlofnologut  .nd  Chief  of  Burr.u 


THE  POTATO-TUBEB   MOTH 

A   PRELIMINARY   ACCOUNT. 


MY 


V.  II.  CHITTENDEN,  s«  .  D.. 

I  top  am/  Stored  Pro 


BUREAU  OF  ENTOMOLOG  V. 

I..  0.  Howard,  Entomologist  and  Chief  of  Bureau. 
C.  L.  Marlatt,  Entomologist  and  Acting  Chief  in  Absence  of  Chief . 

R.  S.  ('UPTON,  Knculin    Assistant. 

\V.  F.  Tastet,  Chief.  Clerk. 

F.  H.  Chittenden,  in  chargt  of  truck  crop  and  store/  ■product  ins,ct  investigations. 

A.  I».  Hopkins,  in  charge  of  forest  insect  investigations. 

W.  D.  Hunter,  in  charge  of  southern  field  crop  insect  investigations. 

V.  M.  Webster,  in  chargt  of  cereal  and  forage  insert  investigations. 

A.  L.  Quaintance,  in  churn,  of  deciduous  fruit  insect  investigations. 

E.  F.  Phillips,  in  chargt  of  bet  culture. 

I).  M.  Rogers,  in  dung,  ,,j  prevt  nting  spread  of  moths,  field  work. 

Rolla  P.  Currik.  in  charge  of  editorial  work. 

Mabel  Colcord,  in  charge  of  library. 

Truck  ('nor  and  Stored  Product  [nsect  [nvestioations. 

F.  II.  Chittenden,  in  charge. 

II.  M.   Russell,  C.  H.  Popenoe,  Wm.  B.  Parker,   II.  0.  Marsh,  M.  M.  High, 
Fred  A.  Johnston,  D.  E.  Fink,  John  E.  Graf,   A    B.   Duckett,  entomological 

assistants. 
I.J.  Condit,  collaborator  in  California. 
W.  X.  (Inn,  collaborator  in  Oregon. 
THOS.  II.  JoNES,  collaborator  in  Porto  Rico. 

Marion  'I'.  Van  Horn,  Pauline  M.  Johnson,  Anita  M.  Ballinger,  preparalors. 
ii 


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Circular  No.  162. 


United  States  Department  of  Agriculture, 

BUREAU   OP   KNTOMOLOGY. 

1      O     HOWARD     1   '  ■  ■"ul  Chief  of  Hureau. 


I  Ml.  POTATO-T1  BER    MOTH. 

/■-     .  /         i  /.ill 

I     ||    Qhittbnden,  Si     D 

I  \  i  i:<  iin  (  n  >t:i  . 

For  m;iii\    years  the  potato-tuber  moth,  known  scientifically    as 

Phthorimxa  opercuhlla    Zell.,    has    I n    the    worsj    potato    pesl    in 

California.  Ii  has  now  reached  the  State 
,.i'  Washington  and  menaces  adjacent 
States.  This  insecl  feeds  also  upon  to-% 
mato,  eggplant,  and  tobacco,  which  'I" 
not.  however.as  a  rule,  suffer  much  injury. 
When  ii  occurs  on  tobacco  ii  is  known  as 
the  splitworm. 

The  mature  moth  of  this  species,  which 
is  quite  small  and  grayish  in  color,  is 
shown  in  6gure  I,  a;  the  Ian  a  is  shown  in 
b  and  c;  and  the  pupa  in  </.  Si/..'-  are  in- 
dicated by  the  size  lines  in  the  figure. 

The  eggs  mas  be  laid  upon  the  le&\  es  oi     i 

■ 

■  ■[.) 


0$ 

0 

*3L i — ~*-~2* 


It   is  believed  thai   there 


on  other  part-  of  the  plant-,  and   the  mi 

ante  caterpillars  or  worms  quickly  bore 

between  the  surfaces  of  the  leave-  or  into 

the  potatoskin,  which  they  mine  in  every 

direction,  finally  devouring   the  exterior. 

are  two  or  more  generations  in  the  course  of  a  summer,  and  certainly 

another  one  can  be  produced  in  store.    It  tint- happen- that  tlusmsecl 

belongs  to  both  truck-crop  and  stored-producl  insecl  pests. 

An  example  of  injury  by  this  species  to  potatoes  is  shown  in  figure 
_>.     At  a  isasection  showing  the  eggs  at  the  top;  at  h,  a  badly  mfesti  d 

I  will 

in'  . 


THE    l'OTVio    I  iki.i:    MOTH. 


potato  in  section;  at  the  left  is  a  section  containing  two  pits,  (Zand 
/,  in  which  the  larva  lias    been    at    work,  while   at    l>  and  c  are  shown 
t  he  egg,  highly  magnified. 

DISTRIBUTION. 

This  species  is  widespread  in  its  distribution,  but  in  this  country, 
mil  il  the  present  year  (1912),  we  did  not  know  of  its  rapid  dissemina- 
tion. Abroad  it  is  well  known  in  Hawaii,  all  portions  of  Australia, 
New  Zealand.  Algeria,  and  many  other  countries,  including  southern 
Europe.  As  an  enemy  to  tobacco  it  has  been  known  for  several 
years  in  Florida  and  in  North  Carolina,  South  Carolina,  and  Virginia.1 

The  directions  for  applying  remedies 
which  follow  are  for  the  benefit  of  per- 
sons inquiring  in  regard  to  means  of 
control.  Which  of  these  should  be 
used  can  be  best  determined  by  trial  in 
the  different  localities  under  the  differ- 
ent conditions  in  which  the  insect  ex- 
ists. This  applies  especially  to  the 
question  as  to  the.  best  material  for 
iumigat  ion. 

EVIDENCE    OF    IMPORTANCE. 

As  evidence  of  the  importance  of  the 

pest  a  few  ([notations  or  notes  should  he 
made. 
r<t         Mr.  J.   E.  Graf,   working   under   the 

Fig.  2.-  Work  of  the  potato-tuber  moth:  o,    direction  of  the  writer,  wrote: 
Section  of  tuber,  showing  eye  and  eggs 

deposited  about  il;  6,  egg  in  outline;  e,         In   September.  1012.  ail   unusual   outbreak  of 
egg,  lateral  view;  ,/,/,  mines  of  larva  in     this  pest  occurred  at  El  Motile,  (al.,  due  entirely 

to  a  combination  of  circumstances.  Thousands 
of  acres  of  potatoes  were  planted  in  southern  Cali- 
fornia—many  more  than  the  market  would  stand. 
This  meant  that  the  market  was  continually  clogged  and  the  prices  were  poor,  so  that 
the  crop  was  worked  off  very  slowly.  The  tuber  moth  (Pkthorimeea  operculella)  is 
always  found  here,  but  the  crop  is  generally  handled  so  quickly  and  carefully  that  small 
loss  results.  This  year,  however,  careless  work  and  the  leaving  of  potatoes  in  the 
ground  too  long  have  given  tile  insect  a  tremendous  start,  and  now  its  ravages  are 
greater  than  ever  before.  A  combination  of  the  moth  and  low  prices  has  so  discouraged 
many  of  the  growers  that  they  are  Leavingtheir  potatoes  to  rot.  ami  as  these  are  becoming 
infested  there  will  be  a  great  number  of  moths  wailing  for  the  fall  potatoes.     *    * 

Later,  September  17,  1912,  Mr.  Graf  wrote  in  regard  to  this  species 
that  two  growers  near  El  Monte,  Cal.,  lost  Slid. not)  and  870,000, 
respectively,  on  potatoes  that  year.  Items  of  this  kind  show  the 
necessity  of  investigating  the  problem. 


potato,  a,  Natural  size;  6,  c,  greatly  en- 
larged;  d,  somewhat  reduced.  (Redrawn 
from  Riley  and  Howard.) 


i  it  is  somewhat  doubtful  if  the  splitworm  on  tobacco  ami  the  potato-tuber  moth  are  the  same  insect, 
although  they  appear  to  !«•  identical  according  t"  the  best  authorities  on  the  subject.    This  is  a  matter  to 

be  settled  later. 


I  ill     P0TAT0-T1   BED    M"i  H.  8 

le  from  numerous  similar  complaints,  including  the  usual  nun, 
ber  from  California  for  the  pasl  two  years,  this  species  has  been  pi 
ceivetl  from  Eagle  Lake  and  Hallettsville,  Tex  ;  San  Jo*    Co  ta  Rica; 
-  attle  Auburn,  and  Yakima, Wash. ;  New"}  ork  City,  where  it  hat  not 
become  acclimatized  so  far  as  known;   Fort  Collins,  Colo  :  and  Lari- 
morc,  V  Dak.     These  records  include  onlj  occurrences  on  potato. 

In  the  case  of  the  lasl  report  the  tuber  moth  was  9tated  to  have 
been  imported  into  southern  California  in  potatoes  from  China.     It  is 
doubtful  if  the  species  has  been  introduced  into  North  Dakota,  but 
inquiries  have  been  made  in  regard  t<>  the  danger  of  it-  being  intro 
duced  there  as  well  as  into  Minnesota  and  some  other  Stati 

M  I  nil  s 

The  potato-tuber  moth  is  a  difficull  insect  t"  control.  It  i-  nol 
possible  it)  reach  the  tuber  wofms  in  their  mines  in  the  potatoes  or  in 
the  stalks  or  tubers  growing  in  the  Geld,  which  make-  it  neccssan  to 
proceed  against  the  pesl  l>\  other  methods.  Of  these,  several  must  be 
emplo) ril  to  insure  buc<  i 

The  first  measure  consists  in  the  maintenance  "I  clean  methods  <>f 
cultivation.  This  implies  that  all  infested  potato  plants  and  solana- 
ceous  weeds,  such  as  ground  cherry,  bull  nettles,  horse  nettles,  and 
vol u nt err  potato  plant-,  gro^ ing  in  the  same  vicinity  as  the  potatoes, 
must  be  destroyed.  This  can  be  done  by  prompt  burning  as  soon 
as  insect  infestation  is  manifest.  The  burning  of  the  weed-  will 
eliminate  places  for  the  breeding  of  the  insect  or  for  its  successful 
hibernation.  Domestic  animals  such  as  sheep  and  hogs  are  valuable 
for  the  destruction  of  remnant-  and  may  be  utilized  l>\  merely  turn- 
ing them  into  the  field. 

Crop  rotation,  as  in  mosl  other  cases  of  insect  injury,  is  desirable 
w  here  possible,  and  the  cooperal  ion  of  all  potato  growers  of  the  neigh- 
borhood i-  practically  a  necessity.  In  certain  cases,  as,  for  example, 
in  a  county  where  many  potatoes  are  grown,  it  mighl  l>e  |><>--il>le  l>\ 
legislat  ion  to  enforce  the  discontinuance  of  potato  planting  for  a  year, 
requiring  at  the  same  time  the  destruction  of  the  weed-  which  serve  as 
I'ood  plant-.  There  are  several  alternate  food  crops  which  do  not 
suffer  materially  from  this  insect.  About  the  best  of  these  are 
Leguminous  crop-,  like  beans,  peas,  cowpeas,  alfalfa,  and  clover. 
These  possess  a  dual  value,  as  the)  all  ad  as  soil  restorers.  Sugar 
beets,  celery,  and  crucifers  are  also  good  as  alternate  food  crops. 
Grains  may  serve  in  the  same  way,  as  they  are  not  attacked  by  the 
tuber  moth.  Care  in  digging  i-  ad\  isable  in  order  not  to  cut  into  t  he 
tuber  or  leave  dug  potatoes  in  the  field  over  night  where  reinfestation 
coidd  occur. 

II    MM,  \I1'"N 

^hile  all  of  these  remedies  are  of  value,  the  best  remedj  i-  the 
fumigation  of  infested  tubers  u  ith  bisulphid  of  carbon  or  hj  drocj  anic- 


4  j  II  K    I'll  I  A  I  ti-  I  I'KKl;     MOTH. 

acid  gas.  If  bisulphid  of  carbon  is  used,  it  should  be  at  the  rate  of 
3  pounds  to  1,000  cubic  feel  of  air  space,  including  the  potatoes; 
1  ounce  to  a  barrel  of  96  pounds'  capacity  would  not  be  excessive. 
With  an  exposure  of  not  more  than  2  l  hours,  no  harm  should  be  done 
to  the  potatoes  for  planting.     The  bisulphid  should  be  evaporated  in 


Fig.  3.— Fumigator  used  for  stored  products  infested  by  insects.    (Author's  illustration. ) 

tins,  like  pie  plates,  and  a  cover  should  be  placed  on  the  top  of  the 
fumigating  barrel  or  box  so  as  to  make  it  as  nearly  air-tight  as  possi- 
ble. At  the  end  of  24  hours  the  potatoes  should  be  removed,  placed 
in  a  fresh  barrel,  and  closed  up. 

Where  it  can  be  conveniently  done  hydrocyanic-acid  gas  should 
be  used  in  a  specially  constructed  fumigator  (see  fig.  3),  also  Lras- 


I  ill     P01  HO    ii  in  i:    \l'»i  ii. 

tight.  In  ill'-  case  of  bisulphid  of  carbon  there  i-^  great  danger  in 
bringing  the  chemical  into  proximity  i"  fire,  Buch  as  a  lighted  lantern 
or  cigar,  for  the  gaa  is  1 1 1  ■_•■  1 1 1  v  inflammable  and  even  explosive.  Thin, 
too,  the  bisulphid-of-carbon  method  costs  Blight!}  more  than  tin- 
bydroc}  anic-acid-gas  method. 

Fumigation  with  hydrocyanic  acid  :_ra>,  properh  performed,  is 
nol  dangerous,  but  it  improperl}  performed  is  decidedly  dangerous 
to  human  and  other  animal  life,  a>  the  fumes  are  ven  poisonous  and 
me  deadh  when  inhaled  in  an\  amount.  This  gaa  i->  more  penc 
trating  than  bisulphid  of  carbon  and  can  !><•  used  l>\  an  intelligent 
person  without  trouble,  it  he  first  familiarizes  himself  thorough!} 
with  the  procedure  by  careful!}  studying  the  printed  directions  or 
assisting  some  one  who  has  bad  experience  in  this  work.  The  cubic 
contents  <>l*  the  receptacle  t"  be  fumigated,  on  which  is  based  the 
amount  of  chemicals  to  l>e  used,  can  be  readil}  computed. 


i  ii  i    i  n\8TH \    i)l     \    ii  mil  . 


A  building,  box,  or  room  (see  fig.  3)  of  about  100  to  200  bushels' 
capacity  suitable  for  the  fumigation  of  a  quantity  of  potatoes  would 
contain  about   500  cubic  feet.     A  fumigator  of  1 1 1  i—  cubic  capacity 

might  In'  built  8  feet  square  b\  8  feet  in  height.     A  _r I,  and  perhaps 

the  best,  means  of  preventing  the  escape  of  the  gas  would  be  to  line 
the  fumigator  with  sheet  tin,  with  soldered  joints,  and  over  sheathing. 
Another  method  would  be  to  sheath  the  room  inside,  cover  the  walls, 
ceiling,  and  floor  with  tarred  or  heav}  building  paper,  with  joints 
well  lapped,  and  cover  the  inside  with  matched  ceiling  boards.  The 
fumigator  should  always  be  equipped  with  a  tight  door  in  which  the 
joints  have  been  broken,  similar  to  the  door  of  a  refrigerator  or  safe, 
and  should  (lose  with  two  refrigerator  catches  against  a  thick  felt 
w.athcr  >tri|>,  which  should  render  it  practical!}  gas-tight.  Thus 
constructed  it  would  furnish  sufficient  space  for  the  fumigation  if 
about  200  bushels  of  material.  There  would  also  be  sufficient  spaoe 
for  the  application  and  diffusion  of  the  hydrocyanic-acid  gas,1  carbon 
bisulphid,  or  other  fumigant  from  the  top  with  a  charge  more  than 
necessary  for  the  quantity  of  potatoes  treated. 

Approved : 

James  Wilson, 

?<  cretary  <>f  A<p  u  ultun  . 

Washington,  D.  C,  September  SO,  1912. 

i  a  rh  hydi 
anyone  who  requests  It,  stating  that  il  ed  f- >r  the  potato-tuba  n 

o 


UNIVERSITY  OF  FLORIDA 


3  1262  09216  6072 


